Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$206.93	4.579%	$216.4053	$216.41	$216.40	$216.40
Purchase #2	$95.87	9.850%	$105.3132	$105.31	$105.30	$105.30
Purchase #3	$196.91	7.479%	$211.6369	$211.64	$211.65	$211.60
Purchase #4	$242.35	4.579%	$253.4472	$253.45	$253.45	$253.40
Purchase #5	$81.45	8.417%	$88.3056	$88.31	$88.30	$88.30
Purchase #6	$108.28	8.204%	$117.1633	$117.16	$117.15	$117.20
Purchase #7	$201.46	3.529%	$208.5695	$208.57	$208.55	$208.60
7 purchase totals =	$1,133.25		$1,200.8410	$1,200.85	$1,200.80	$1,200.80